The present invention relates to an acutating knob, particularly for the window crank of an automotive vehicle.
An actuating knob of this type is shown in Federal Republic of Germany Utility Model (Gebrauchsmuster) No. 73 03 571. This actuating knob has an outer relatively soft knob part and an inner load-bearing knob part of relatively hard material which serves as a pivot pin. This arrangement is intended to avoid impact injuries which might occur upon automobile accidents. However, experience has shown that the elasticity of the material itself is insufficient in practically all cases to achieve the necessary damping and counteracting of an impact, for instance, with the head, knee, etc.
In another actuating knob shown in Federal Republic of Germany Utility Model No. 19 50 978, a connection adapted to release upon lateral pressure on the knob is provided between the knob and the connecting part. The knob is intended to loosen automatically from its mount under an impact force and to drop off. This also has defects. Very narrow tolerances must be maintained, and this complicates the manufacture and makes it more expensive. However, even if narrow tolerances are maintained, the desired effect is not reliably assured, since the plastic material of which operating knobs are generally produced expands at high temperatures and contracts at low temperatures. Accordingly, despite increased impact force, the actuating knob might not release from its mount and would cause impact injuries. It is also possible for the knob to become unintentionally loosened upon actuation and be lost. This known actuating knob has the further advantage that the shaft section of the knob is seated in a borehole in the crank arm. The knob engages, by means of a collar-like widening, over the end surface of the bore hole, which faces away from the knob. This secures the knob in the axial direction. Upon a tilting moment being applied to the knob, which is unavoidable upon actuation of the crank, the collar cannot prevent canting of the shaft in the borehole and cannot prevent the increased bearing friction caused by the tilting moment. The radial component of force which applies the tilting moment acts on a lever arm which extends from the actuating knob up to the end of the borehole facing away from the knob. The tilting moment and the disturbing impairment in the slidability of the shaft in the support borehole of the crank arm increase with the length of this lever arm.